Liangyin Chen

Group-based discovery in low-duty-cycle mobile sensor networks

Wireless Sensor Networks have been used in many mobile applications such as wildlife tracking and participatory urban sensing. Because of the combination of high mobility and low-duty-cycle operations, it is a challenging issue to reduce discovery delay among mobile nodes, so that mobile nodes can establish connection quickly once they are within each others vicinity. Existing discovery designs are essentially pair-wise based, in which discovery is passively achieved when two nodes are pre-scheduled to wake-up at the same time. In contrast, for the first time, this work reduces discovery delay significantly by proactively referring wake-up schedules among a group of nodes. Because proactive references incur additional overhead, we introduce a novel selective reference mechanism based on spatiotemporal properties of neighborhood and the mobility of the nodes. Our quantitative analysis indicates that the discovery delay of our group-based mechanism is significantly smaller than that of the pair-wise one. Our testbed experiments using 40 sensor nodes confirm our theoretical analysis, showing one order of magnitude reduction in discovery delay compared with traditional pair-wise methods with only 0.5%~8.8% increase in energy consumption.

Group-Based Neighbor Discovery in Low-Duty-Cycle Mobile Sensor Networks

Wireless sensor networks have been used in many mobile applications such as wildlife tracking and participatory urban sensing. Because of the combination of high mobility and low-duty-cycle operations, it is a challenging issue to reduce discovery delay among mobile nodes, so that mobile nodes can establish connection quickly once they are within each others vicinity. Existing discovery designs are essentially pairwise based, in which discovery is passively achieved when two nodes are prescheduled to wake up at the same time. In contrast, this work reduces discovery delay significantly by proactively referring wake-up schedules among a group of nodes. Since proactive references incur additional overhead, we introduce a novel selective reference mechanism based on spatiotemporal properties of neighborhood and the mobility of nodes. Our quantitative analysis indicates that the discovery delay of our group-based mechanism is significantly smaller than that of the pairwise one. Our testbed experiments using 40 sensor nodes and extensive simulations confirm the theoretical analysis, showing one order of magnitude reduction in discovery delay compared with legacy pairwise methods in dense, uniformly distributed sensor networks with at most 8.8 percent increase in energy consumption.

Lightning: A High-Efficient Neighbor Discovery Protocol for Low Duty Cycle WSNs

In wireless sensor networks (WSNs), due to the limited energy of nodes, discovering neighbors needs to be achieved in an energy-efficient way. This means that, at a given energy consumption, we need to reduce the worst-case neighbor discovery latency as far as possible. In this letter, we propose a novel deterministic neighbor discovery method, called Lightning. Lightning employs two kinds of active slots of different active lengths (we call A slot and C slot, respectively). The active time of C slot is much shorter than that of A slot in order to reduce the energy consumption. In addition, to maximize the energy efficiency, Lightning adopts one-way neighbor discovery method. This makes C slot have the smallest active length that is only enough to send one beaconing packet. Through proactively sending one beaconing packet after one-way discovery, Lightning also realizes bi-directional neighbor discovery. The theoretical analysis indicates that, with the same energy consumption, our method reduces the worst-case latency bound up to 37.9% compared with Searchlight-Trim, the best existing discovery algorithm. The simulation verifies the soundness and effectiveness of our design.

Poster: Selective reference mechanism for neighbor discovery in low-duty-cycle wireless sensor networks

Based on spatiotemporal properties of neighborhood and mobile properties of nodes in the networks, we propose Selective Reference Mechanism to trade off between the delay and overhead of neighbor discovery in low-duty-cycle WSNs. Extensive simulation and test-bed experiment confirm our theoretical analysis, showing as much as 35.4% increase in discovery probability, 38.6% reduction in discovery delay and 27.7% reduction in total energy consumption.

TH-C-217BCD-01: Best in Physics (Imaging) - Evaluation of Apoptosis and Proliferation in Non-Thermal Pulsed HIFU Treated Mouse Prostate Tumors

Purpose: The underlying mechanism of non‐thermal effects of pulsed high intensity focused ultrasound (pFUS) on normal and tumor tissues is not well understood. Our recent studies showed significant prostate cancercell killing in vitro and significant prostate tumorgrowth delay in vivo after pFUS treatment. We hypothesized that these effects of non‐thermal pFUS are due to an increase in cell apoptosis and decrease in cell proliferation. Therefore, the purpose of this study was to analyze the biomarkers of apoptosis and proliferation in prostate tumors after pFUS exposures. Methods: An orthotopic prostate tumor model was established in nude mice. Prostate tumors were sonicated with MR guided pFUS (1MHz, 5W acoustic power, 5Hz frequency; 0.1duty cycle) for 60 sec for each sonication with temperature <42°C (InSightec ExAblate 2000 with a 1.5T GE MR scanner). Untreated tumors were used as controls. The mice were sacrificed at predetermined times up to 7 days following therapy. Tumors were processed for light microscopic examination with H&E staining and immunohistochemical staining for caspase 3 (a marker of apoptosis) and Ki67 (aproliferation marker) expression. Results: Light microscopy revealed the absence of thermal damage and acute destruction of tumor tissues exposed to pFUS. The microvessel walls in the tissues remained intact. There was no change in the extent of hemorrhage upon pFUS treatment over time. The apoptotic index, defined as a percentage of apoptotic cells per total number of cells, peaked at 24 hours after FUS treatment relative to control. There was no dramatic difference in the proliferation indices between different time points. Conclusions: Our results suggested that non‐thermal pulsed pFUS induced caspase 3‐mediated apoptosis and did not produce any thermal damage in the prostate tumor tissues. We are performing additional studies to evaluate blood vessel density and cellular DNA damage upon pFUS treatment.

Twice Deployment Node Balance Algorithm for Road Network Surveillance

This paper proposes a twice deployment node balance algorithm (TDNB) which guarantees successful detection of the moving target on road networks. Through dividing the deployment of the sensor nodes into two phases instead of deploying all the sensors at one time, TDNB has a better performance. In the former phase, some of the sensors are deployed on the road at random. In the latter phase, the rest of the sensors are deployed on demand to make the number on each path the same. Due to the equivalence of the nodes number, the network will have a prolonged lifetime after inserting nodes into the segment according to this algorithm. TDNB extends the networks lifetime remarkably compared with the former algorithms. Furthermore, TDNB enables us to insert nodes to the segment required in the network instead of all the segments, which reduces the workload to a large extent. In short, without increasing the number of sensors in road network, TDNB has a better performance compared to VISA in terms of network lifetime, which meets the demand for persistent monitoring application.

WE-E-220-05: On-Thermal Pulsed Focused Ultrasound for Cancer Therapy

Purpose: MR guided focused ultrasound (MRgFUS) has been investigated for ablative therapy and drug enhancement for gene therapy and chemotherapy in our institution. The aim of this work is to explore the feasibility of pulsed focused ultrasound (pFUS) for non‐thermal cancer therapy using an in vivo animalmodel. Methods: An InSightec ExAblate 2000 with a 1.5T GE MR scanner was used in this study. Suitable ultrasound parameters were investigated to perform non‐thermal sonications, keeping the temperature below 42C as measured in real time by MR thermometry. LNCaP cells (106) were injected into the prostates of male mice (n=20). When tumors reached the volume of 100±50mm3 on MRI, the tumor‐bearing mice (n=8) were treated with pFUS (US frequency 1MHz; 25W acoustic power; pulse frequency 1Hz; 0.1 duty cycle) for 60sec. A total of 4–6 sonications were used to cover the entire tumor volume under MR image guidance. The animals were allowed to survive for 4 weeks after the treatment. The tumor growth was monitored on MRI and compared with the control group (n=12). Results: Significant tumor growth delay was observed in the tumor‐bearing mice treated with pFUS. The mean tumor volume for the pFUS treated mice remained the same 1 week after the pFUS treatment while the mean tumor volume of the control mice grew 42% over the same time. Two weeks after the pFUS treatment the cont Conclusions: Our results demonstrated that non‐thermal pFUS has a great potential for cancer therapy. Further experiments are needed to derive optimal ultrasound parameters and fractionation schemes to maximize the therapeutic effect. This work is supported by Focused Ultrasound Surgery Foundation, Varian Medical Systems, DOD PC073127 and DOD BC102806. Technical support from InSightec is acknowledged.

A Fast Neighbor Discovery Algorithm in WSNs

With the quick development of Internet of Things (IoT), one of its important supporting technologies, i.e., wireless sensor networks (WSNs), gets much more attention. Neighbor discovery is an indispensable procedure in WSNs. The existing deterministic neighbor discovery algorithms in WSNs ensure that successful discovery can be obtained within a given period of time, but the average discovery delay is long. It is difficult to meet the need for rapid discovery in mobile low duty cycle environments. In addition, with the rapid development of IoT, the node densities of many WSNs greatly increase. In such scenarios, existing neighbor discovery methods fail to satisfy the requirement in terms of discovery latency under the condition of the same energy consumption. This paper proposes a group-based fast neighbor discovery algorithm (GBFA) to address the issues. By carrying neighbor information in beacon packet, the node knows in advance some potential neighbors. It selects more energy efficient potential neighbors and proactively makes nodes wake up to verify whether these potential neighbors are true neighbors, thereby speeding up neighbor discovery, improving energy utilization efficiency and decreasing network communication load. The evaluation results indicate that, compared with other methods, GBFA decreases the average discovery latency up to 10.58% at the same energy budget.

Trajectory-Based Hierarchical Adaptive Forwarding in Vehicular Ad Hoc Networks

This paper proposes a Trajectory-Based Hierarchical Adaptive Forwarding (THAF) scheme, tailored and optimized for the efficient multihop vehicle-to-vehicle (v2v) data delivery in vehicular ad hoc networks. We utilize the trajectories of vehicles provided by GPS-based navigation systems to predict forward delay and access area in a privacy-preserving manner. Different from existing trajectory-based forwarding schemes, we establish a hierarchical VANET topology to optimize forwarding path and adopt adaptive diffusion strategy to forward data in light-traffic situations. Through theoretical analysis and extensive simulation, it is shown that our design performs better than the existing schemes.

SU-E-J-01: MR Guided Pulsed Focused Ultrasound Mediated Targeted Chemotherapeutic-Agent Delivery in Management of Prostate Cancer

Purpose: The purpose of this study is to investigate an innovative approach to prostate cancer therapy using nanodroplet-encapsulated drugs combined with pulsed high intensity focused ultrasound (pFUS) treatment. Pulsed FUS treatment improves localized drug release from the carrier and enhances intracellular uptake, which ensures temporal and spatial control of local drug delivery while reducing systemic toxicity from the drugs. Methods: LNCaP cells were implanted into the prostates of nude mice. Tumor growth was monitored using MRI. The tumor—bearing mice were randomly divided into 5 groups (n=5 for each group). Group 1, animals were treated with an IV injection of docetaxel (DTX)-encapsulated nanodroplets (ND-DTX) + pFUS. Animals in Group 2 were treated with pFUS alone. Animals in Group 3 were injected (IV) with DTX-encapsulated nanodroplets alone, Group 4 received free DTX alone and Group 5 was used as a control group. After treatment, animals were allowed to survive for 3 weeks. Tumor growth delay was monitored by MRI (resolution: <0.2mm). The formulation of the DTX-encapsulated nanodroplets was: DTX dose 20 mg/kg, Nanoemulsion composition 0.5% PTX, 1% perfluorocarbon and 2% stabilizing block copolymer. Ultrasound treatment parameters were 1MHz, 25W acoustic power, 10% duty cycle and 60 sec for each sonication. Results: Our results showed that Group 1, in which animals were treated with an IV injection of ND-DTX + pFUS, exhibited the most tumor growth control (50%–30%) among all groups. All other groups showed similar tumor growth to that of the control group after the treatment (within statistical uncertainties). Conclusion: Our preliminary results showed a great potential for prostate cancer therapy using targeted DTX+ nanodroplets, which could be activated by pFUS. Further animal studies are warranted to confirm the results. The enhancement effect of pFUS on targeted drug delivery needs to be investigated quantitatively.